Recently Vestergaard (2002) has developed an empirical
method for estimating the masses of black holes in active
galactic nuclei (AGNs) based on rest-frame ultraviolet
spectral properties (broad C IV line width and UV continuum
luminosity). The primary application of this method is for
high-redshift quasars, for which the better established
optical mass estimators (broad H-beta line width and optical
continuum luminosity) are redshifted into the
more-difficult-to-observe near-infrared. Vestergaard's
empirical method is based on relatively low-luminosity
quasars at low redshift and has not been explicitly tested
for a significant number of high-luminosity quasars at
high-redshift. We have compiled approximately 50 luminous
high-z quasars for which both C IV and H-beta profiles are
available and used these to estimate black hole masses.
While there is significant scatter, the ratio of black hole
mass estimates for the sample is consistent with unity,
indicating that there is no systematic problem extrapolating
C IV-based mass estimates into this region of parameter
space. We find no systematic trends between either the C IV
blueshift or the line width and the ratio of mass estimates.
Finally, we have estimated the Eddington ratio, L/LEdd,
and find that for this region of parameter space values
ranging from a few percent to marginally super-Eddington. In
particular, broad absorption line (BAL) quasars span the
full range of Eddington ratios with no clear distinction
from the other luminous quasars examined.

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